We show that fused deposition modelling (FDM) 3D-printed electrodes can be used for quality control of fuel bioethanol. 3Dprinting using carbon black/polylactic acid (CB-PLA) filaments resulted in conductive and biodegradable electrodes for biofuel analysis. As a proof-of-concept, copper determination in fuel bioethanol was performed, as such ions catalyse oxidation processes during storage and transport. Square-wave anodic-stripping voltammetry (SWASV) of copper was achieved after sample dilution in 0.1 mol L −1 HCl as supporting electrolyte (resulting in 30:70% v/v ethanol:water). The linear responses were in the range between 10 and 300 μg L −1 (R = 0.999), inter-day precision was lower than 8% (n = 10, for 20 μg L −1 ) and limits of detection (LOD) and quantification (LOQ) using 180 s as deposition time were 0.097 μg L −1 and 0.323 μg L −1 , respectively. Recovery values between 95 and 103% for the analysis of bioethanol spiked with known amounts of copper were obtained. These results show great promise of the application of 3D-printed sensors for the quality control of biofuels.
Additively manufactured sensors have
shown promising features regarding
sustainability, because of the reduction of waste, feasible use of
biopolymers, the fabrication process, and large-scale production.
Graphene-integrated polylactic acid (G/PLA) is an excellent material
to three-dimensional (3D)-print electrochemical sensors with outstanding
stability, robustness, and sensitivity. Herein, we propose 3D-printed
G/PLA electrochemical sensors to the monitoring of quality control
of biodiesel and/or biokerosene, which have been widely demanded worldwide
to replace fossil fuels. The main drawback of such biofuels is their
oxidation instability, which can be controlled by the monitoring of
additive antioxidants added to retard oxidation processes. This is
the first application of a 3D-printed sensor for such biofuels, and
as a proof-of-concept, we demonstrate that these sensors can determine tert-butylhydroquinone (TBHQ), the most used antioxidant
in biofuels, in soybean biodiesel and coconut biokerosene. TBHQ is
electrochemically oxidized at +0.3 V (vs Ag|AgCl|KCl(sat.)), and a microliter aliquot of the samples was diluted in 0.12 mol
L–1 Britton–Robinson solution (pH 4.05) containing
sodium dodecyl sulfate to stabilize the emulsion before the voltammetric
measurement. An STL 3D printer and a 3D pen were used to fabricate
the sensors in a cylindrical shape (3.5 cm length × 0.4 cm diameter).
After selecting optimal parameters, the sensor presented a linear
range up to 400 μmol L–1 (r > 0.99) and a detection limit estimated as 0.1 μmol L–1. High precision was attested by relative standard
deviation values lesser than 5% (interday and interelectrode measures).
The metallic species Fe3+, Pb2+, Cu2+, Mn2+, and Cr2+, which can be found because
of corrosion of metallic parts by the action of storing and transporting
biofuels, did not statistically interfere (t
tab = 1.833 > t
cal = 0.114)
in
the determination of TBHQ. The analysis of samples spiked with TBHQ
resulted in recovery values that ranged from 86 to 105%. A commercial
biodiesel sample was analyzed by both the proposed and high-performance
liquid chromatography methods, and the results were statistically
similar. Importantly, the sensor was compatible with biofuels, and
its surface can be renewed after polishing for its continuous use
for routine applications.
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